Copolymer having low isoprenoid content

ABSTRACT

A copolymer has low levels of isoprenoid (short chain branching) structures. A process for producing the copolymer having low isoprenoid content involves contacting at least one isoolefin monomer with at least one multiolefin and/or β-pinene monomer in the presence of at least one Lewis acid and at least one initiator in a diluent. The diluent may contain a hydrofluorinated olefin (HFO) comprising at least three carbon atoms and at least three fluorine atoms. Hydrofluorinated olefins used in the present invention are better diluents for butyl slurry cationic polymerization than saturated hydrofluorocarbons. Blends of saturated hydrofluorocarbons (e.g. 1,1,1,2-tetrafluoroethane) with an inert solvent (e.g. methyl chloride) may also be used as diluents.

FIELD OF THE INVENTION

This application relates to copolymers of an isoolefin and a multiolefinand to processes for production thereof comprising a hydrofluorinatedolefin (HFO) diluent.

BACKGROUND OF THE INVENTION

Butyl rubber (IIR), a random copolymer of isobutylene and isoprene iswell known for its excellent thermal stability, ozone resistance anddesirable dampening characteristics. IIR is prepared commercially in aslurry process using methyl chloride as a diluent and a Friedel-Craftscatalyst as the polymerization initiator. The methyl chloride offers theadvantage that AlCl₃, a relatively inexpensive Friedel-Crafts catalyst,is soluble in it, as are the isobutylene and isoprene comonomers.Additionally, the butyl rubber polymer is insoluble in the methylchloride and precipitates out of solution as fine particles. Thepolymerization is generally carried out at temperatures of about −90° C.to −100° C. (see U.S. Pat. No. 2,356,128 and Ullmanns Encyclopedia ofIndustrial Chemistry, volume A 23, 1993, pages 288-295, the entirecontents of each of which are herein incorporated by reference). The lowpolymerization temperatures are required in order to achieve molecularweights which are sufficiently high for rubber applications.

Recently there has been an emphasis on finding alternative diluents tothe traditional chlorinated hydrocarbon, methyl chloride.Hydrofluorocarbons (HFC's) have similar properties to chlorinatedhydrocarbons and are known refrigerants (see WO 2008/027518 and WO2009/042847). Such HFC's, especially saturated HFC's, for exampleHFC-134a (1,1,1,2-tetrafluoroethane), have been identified as potentialreplacements for methyl chloride in polymerization processes involvinghigher temperatures (see U.S. Pat. No. 7,723,447, U.S. Pat. No.7,582,715, U.S. Pat. No. 7,425,601, U.S. Pat. No. 7,423,100, U.S. Pat.No. 7,332,554, U.S. Pat. No. 7,232,872 , U.S. Pat. No. 7,214,750, U.S.Pat. No. 7,699,962, US 2008/0290049, U.S. Pat. No. 7,781,547, U.S. Pat.No. 7,342,079, US 2007/0117939, US 2007/0299190, US 2007/0299161, US2008/0234447, US 2008/0262180, U.S. Pat. No. 7,414,101, U.S. Pat. No.7,402,636 and U.S. Pat. No. 7,557,170).

However, such saturated HFC's are strong greenhouse gases and their useis undesirable. The most studied HFC is HFC-134a(1,1,1,2-tetrafluroethane), also known as R134a, which has been broadlycommercialized as a refrigerant in the 1990's to replacechlorofluorocarbons (CFC's) and hydrochlorofluorocarbons (HCFC's), whichare ozone-depleting chemicals. The expanding use of HFC-134a is nowposing a significant environmental threat as such HFC's are known to bepowerful greenhouse gases. The GWP (Global-Warming Potential) ofHFC-134a is 1430. There have been several discussions internationally toimplement a controlled program to phase out of HFC-134a.

Further, cyclic oligomers are formed in significant quantities in butylpolymerization using either HFC-134a or methyl chloride as diluents ortheir blends thereof. These impurities are undesirable forpharmaceutical applications, such as rubber closures, due to thepotential to extract the oligomers from the rubber. Furthermore,isoprenoid (short chain branching) structures are formed in significantquantities in butyl polymerization using methyl chloride as diluent.Isoprenoid structures limit the efficiency of subsequent halogenationreactions when producing halobutyl rubbers. Furthermore, when highisoprene butyl rubber is desired, traditional reactions require carefulcontrol of process conditions to increase isoprene levels in the butylrubber.

Thus, there is still a need for polymerization vehicles that arerelatively inexpensive, are not strong contributors to the greenhouseeffect and/or provide improvement to the polymerization process. Thereis also still a need for butyl polymers having low levels of cyclicoligomers, low levels of isoprenoid structures and/or high levels ofisoprene.

SUMMARY OF THE INVENTION

It has now been surprisingly found that a particular class of HFC's, thehydrofluorinated olefins (HFO's), and in particular the class of HFO'sknown as tetrafluorinated propenes, are an excellent medium for butylrubber slurry polymerization processes. There is provided a process forproducing a copolymer, comprising: contacting at least one isoolefinmonomer with at least one multiolefin and/or β-pinene monomer in thepresence of at least one Lewis acid and at least one initiator in adiluent comprising a tetraflourinated propene. There is further provideda copolymer produced by a process of the present invention.

It has also been surprisingly found that blends of HFO's and other inertsolvents in butyl rubber slurry polymerization processes result inpolymers having low levels of isoprenoid (short chain branching)structures. There is provided a process for producing a copolymer,comprising: contacting at least one isoolefin monomer with at least onemultiolefin and/or β-pinene monomer in the presence of at least oneLewis acid and at least one initiator in a diluent comprising a blend ofa tetraflourinated propene and an inert solvent other than thetetraflourinated propene.

When certain HFO's are used as diluents, these processes advantageouslyresult in polymers having high levels of multiolefin incorporatedtherein. There is provided a copolymer of at least one isoolefin monomerand at least one multiolefin and/or β-pinene monomer having amultiolefin and/or β-pinene monomer content higher than a comparablepolymer produced in a butyl rubber slurry process using1,1,1,2-tetrafluoroethane as a diluent.

When certain HFO's are used as diluents, these processes advantageouslyresult in polymers having low levels of cyclic oligomers and/or polymershaving advantageously low ratios of C21/C13 oligomers. There is provideda copolymer of at least one isoolefin monomer and at least onemultiolefin and/or β-pinene monomer having a cyclic oligomer content atleast 10% lower than a comparable polymer produced in a butyl rubberslurry process using 1,1,1,2-tetrafluoroethane as a diluent.

When certain HFO's are used as diluents, these processes advantageouslyresult in polymers having low levels of isoprenoid (short chainbranching) structures. There is also provided a copolymer of at leastone isoolefin monomer and at least one multiolefin and/or β-pinenemonomer having an isoprenoid content lower than a comparable polymerproduced in a butyl rubber slurry process using1,1,1,2-tetrafluoroethane as a diluent.

A copolymer may be produced according to a process comprising:contacting at least one isoolefin monomer with at least one multiolefinand/or β-pinene monomer in the presence of at least one Lewis acid andat least one initiator in a diluent. A copolymer may be produced at atemperature of less than or equal to −75° C. or less than or equal to−95° C. The diluent preferably comprises a hydrofluorinated olefin (HFO)comprising at least three carbon atoms and at least three fluorineatoms. The diluent may comprise at least three carbon atoms and/or atleast four fluorine atoms. A preferred diluent comprises four fluorineatoms. A particularly preferred diluent is of the class known astetrafluorinated propenes, comprising three carbon atoms and fourfluorine atoms.

Hydrofluorinated olefins comprising tetraflourinated propenes are betterdiluents for butyl slurry cationic polymerization than saturatedhydrofluorocarbons. For example HFO-1234yf(2,3,3,3-tetrafluoro-1-propene) was found to be surprisingly a muchbetter diluent for butyl slurry cationic polymerization than HFC-134a(1,1,1,2-tetrafluoroethane), especially at low temperature (e.g. −95°C.), but also at elevated temperature (e.g. −75° C.). Use oftetraflourinated propenes (e.g. HFO-1234yf) as a diluent provides one ormore of the following advantages: higher polymer yield; highermultiolefin incorporation; higher molecular weight polymer chains;narrower molecular weight distribution; lower cyclic oligomerby-products; a more favourable ratio of C21/C13 cyclic oligomers; and/ora lower isoprenoid (short chain branching) structure content.

Copolymers may contain significantly lower isoprenoid content than butylrubber produced in 1,1,1,2-tetrafluoroethane, indicating decreased shortchain branching resulting from polymer back-biting reactions during thepolymerization. A butyl rubber with a lower isoprenoid content will havea higher proportion of total unsaturations available in a 1,4-unitorientation for further chemical modification, and is expected to havehigher efficiency in subsequent halogenation reactions in order toproduce halobutyl rubber. The isoprenoid content may be less than about15% based on the total unsaturations present in the polymer, preferablyless than about 12%, more preferably about 11% or less, even morepreferably about 6% or less. Total unsaturations is defined as the sumof multiolefin (mol %) and isoprenoid (mol %), where mol % is based ontotal moles of monomer units in the copolymer. Isoprenoid content isdefined as a ratio of isoprenoid (mol %) to total unsaturations (mol %).

The copolymer may have a cyclic oligomer content at least 10% lower thana comparable polymer produced in a butyl rubber slurry process using1,1,1,2-tetrafluoroethane as a diluent. The cyclic oligomer content maybe at least 25% lower, at least 50% lower, at least 60% lower, at least70% lower, or at least 75% lower than a comparable polymer produced in abutyl rubber slurry process using 1,1,1,2-tetrafluoroethane as adiluent. The ratio of C21/C13 oligomers in the copolymer may be lessthan or equal to 2.5, 2.0 or 1.5. Total cyclic oligomer content may beless than 3200 ppm with a ratio of C21/C13 oligomers of less than 1.5.These copolymers may have a cyclic oligomer content of less than orequal to 2000 ppm, less than or equal to 1000 ppm, less than or equal to700 ppm, or less than or equal to 650 ppm.

The copolymer may be dissolved in a solvent suitable for extracting C13cyclic oligomeric products. The solvent may be removed to strip thesolvent and the C13 cyclic oligomeric products from the copolymer. Thesolvent may be non-polar and may comprise an alkane, such as hexane. Thestripping may be conducted at elevated temperature using, for example,steam as a stripping agent. The polymer may be previously dissolved inan alcohol, such as ethanol, prior to the stripping step. The ratio ofC21/C13 oligomers in the polymer prior to stripping may be less than orequal to 7.9, 7.3, 2.5, 1.5 or 1.0.

Formation of cyclic oligomers may be drastically suppressed in thepresence of hydrofluorinated olefins as the diluent, especially at atemperature of −90° C. or lower (e.g. −95° C.). The oligomeric contentof polymers of the present invention may be at least 20% lower, at least30% lower, at least 40% lower, at least 50% lower, at least 55% lower,at least 60% lower, at least 65% lower, at least 70% lower, at least 75%lower, at least 80% lower, at least 85% lower, at least 90% lower and/orup to 95% lower than with other diluents, e.g. HFC-134a and/or methylchloride.

Multiolefin (e.g. isoprene) content of polymers of the present inventionmay be in a range of from 0.5 to 15 mol %, based on the weight of thepolymer. Multiolefin content of polymers may be up to 5-10% greater thanpolymers produced using prior art diluents (e.g. MeCl and/or HFC-134a)at similar temperature and conversion. Higher multiolefin content isespecially evident when comparing the use of HFO-1234yf to HFC-134a,especially at a temperature of −75° C. or lower (e.g. −95° C.). Higherincorporation of multiolefin equates to better utilization of themultiolefin, meaning less waste and lower overall process cost.Incorporation of multiolefin may be compared based on a ratio of feedmonomer composition (f=[M₁]/[M₂]) to copolymer composition(F=[M₁]/[M₂]). The ratio of feed monomer composition to copolymercomposition (f/F) in a process of the present invention is preferablygreater than about 0.7, more preferably greater than about 0.8, evenmore preferably about 0.85 or greater, yet even more preferably about0.9 or greater.

The molecular weights of polymers of the present invention are similarto or significantly higher than the molecular weights of polymersproduced using prior art diluents (e.g. MeCl and/or HFC-134a). At highertemperatures, e.g. around −75° C., the molecular weights are greater,but a temperature of −90° C. or lower (e.g. −95° C.), the molecularweights of the present polymers, especially those produced inHFO-1234yf, can be significantly greater than that of polymers producedin prior art diluents (e.g. MeCl and/or HFC-134a). For example, at −75°C., the weight average molecular weight (M_(w)) may be greater than orequal to 330,000 g/mol or greater than or equal to 400 g/mol, and at−95° C. the molecular weight may be greater than or equal to 445,000g/mol or greater than or equal to 475,000 g/mol. This means that it ispossible to produce a desired molecular weight co-polymer at a highertemperature with tetraflourinated propene diluents, which leads toreduced energy cost, improved process economics and reduced impact onthe environment.

Yield of the polymer produced in the present process may be at leastcomparable to, and in some cases may be over 1.5 times, or even over 2times, the yield obtained using prior art diluents (e.g. MeCl and/orHFC-134a). Higher yields are especially evident when comparing the useof HFO-1234yf to HFC-134a, especially at a temperature of −90° C. orlower (e.g. −95° C.).

Therefore, for a given molecular weight, production at highertemperature is possible using the tetraflourinated propene diluents ofthe present invention, at higher conversion and more efficient isopreneutilization than can be obtained using prior art diluents (e.g. MeCland/or HFC-134a). This surprising combination of advantageous featuresleads to lower overall process costs and improved polymers.

Furthermore, certain HFO's have desirable properties but do not harmozone (Ozone Depleting Potential, ODP=0) and have little or no potentialfor global warming. Examples of these more eco-friendly hydrofluorinatedolefins are the tetraflourinated propenes HFO-1234fy (GWP=4) andHFO-1234ze (GWP=6), which are especially noteworthy as potentialreplacements for HFC-134a (GWP=1430).

Further features of the invention will be described or will becomeapparent in the course of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly understood, embodimentsthereof will now be described in detail by way of example, withreference to the accompanying drawings, in which:

FIG. 1A depicts reaction temperature profile for reactions with purediluent components at −95° C.

FIG. 1B depicts a graph showing molecular weight for polymers producedin various ratios of HFO-1234yf or HFC-134A with MeCl at −95° C.

FIG. 2 depicts a graph of total oligomer content in butyl rubberproduced in MeCl, HFC-134A and HFO-1234yf at standard isoprene levels(2.3 mol % feed ratio).

FIG. 3 depicts a graph of total oligomer content in butyl rubberproduced in MeCl, HFC-134A and HFO-1234yf at high isoprene levels (5.6mol % feed ratio).

FIG. 4 depicts a graph showing C21/C13 oligomer ratio in butyl rubberproduced in MeCl, HFC-134A and HFO-1234yf at −95° C. using various feedisoprene concentrations.

FIG. 5 depicts a graph showing feed monomer ratio (f) as compared tocopolymer ratio (F) for polymerizations performed in MeCl, HFC-134A andHFO-1234yf at various feed isoprene levels.

DESCRIPTION OF PREFERRED EMBODIMENTS

In this specification including the claims, the use of the article “a”,“an”, or “the” in reference to an item is not intended to exclude thepossibility of including a plurality of the item in some embodiments. Itwill be apparent to one skilled in the art in at least some instances inthis specification including the attached claims that it would bepossible to include a plurality of the item in at least someembodiments.

Butyl rubbers are formed by the copolymerization of at least oneisoolefin monomer and at least one multiolefin monomer, and optionallyfurther copolymerizable monomers.

The present invention is not limited to a special isoolefin. However,isoolefins within the range of from 4 to 16 carbon atoms, preferably 4-7carbon atoms, such as isobutene, 2-methyl-1-butene, 3-methyl-1-butene,2-methyl-2-butene, 4-methyl-1-pentene and mixtures thereof arepreferred. More preferred is isobutene.

The present invention is not limited to a special multiolefin. Everymultiolefin copolymerizable with the isoolefin known by those skilled inthe art can be used. However, multiolefins within the range of from 4-14carbon atoms, such as isoprene, butadiene, 2-methylbutadiene,2,4-dimethylbutadiene, piperyline, 3-methyl-1,3-pentadiene,2,4-hexadiene, 2-neopentylbutadiene, 2-methyl-1,5-hexadiene,2,5-dimethly-2,4-hexadiene, 2-methyl-1,4-pentadiene,2-methyl-1,6-heptadiene, cyclopentadiene, methylcyclopentadiene,cyclohexadiene, 1-vinyl-cyclohexadiene and mixtures thereof, preferablyconjugated dienes, may be used. Isoprene is more preferably used.β-pinene can also be used as a co-monomer for the isoolefin.

Any monomer copolymerizable with the isoolefins and/or dienes known bythose skilled in the art can be used as an alternative to theaforementioned multiolefins, or even in addition to the aforementionedmultiolefins. Indene, styrene derivatives or mixtures thereof may beused in place of the multiolefins listed above or as optional additionalmonomers. α-Methyl styrene, p-methyl styrene, chlorostyrene or mixturesthereof are preferably used. p-Methyl styrene is more preferably used.

The polymerization of the butyl polymer is performed in the presence ofa Lewis acid and an initiator capable of initiating the polymerizationprocess. Suitable Lewis acids are those that readily dissolve in theselected diluent. Examples of suitable Lewis acids include ethylaluminum dichloride (EADC), diethyl aluminum chloride (DEAC), titaniumtetrachloride, stannous tetrachloride, boron trifluoride, borontrichloride, methylalumoxane and/or mixtures thereof. In someembodiments, AlCl₃ may also be used. Suitable initiators comprise aproton source and/or cationogen. A proton source suitable in the presentinvention includes any compound that will produce a proton when added tothe selected Lewis acid. Protons may be generated from the reaction ofthe Lewis acid with proton sources such as water, hydrochloric acid(HCl), alcohol or phenol to produce the proton and the correspondingby-product. Such reaction may be preferred in the event that thereaction of the proton source is faster with the protonated additive ascompared with its reaction with the monomers. Other proton generatingreactants include thiols, carboxylic acids, and the like. The mostpreferred Lewis acid comprises a mixture of EADC and DEAC and the mostpreferred proton source is HCl. The preferred ratio of EADC/DEAC to HClis between 5:1 to 100:1 by weight.

In addition or instead of a proton source a cationogen capable ofinitiating the polymerization process can be used. Suitable cationogenincludes any compound that generates a carbo-cation under the conditionspresent. A preferred group of cationogens include carbocationiccompounds having the formula:

wherein R¹, R² and R³, are independently hydrogen, or a linear, branchedor cyclic aromatic or aliphatic group, the proviso that only one of R¹,R² and R³ may be hydrogen. Preferably, R¹, R² and R³, are independentlya C₁ to C₂₀ aromatic or aliphatic group. Non-limiting examples ofsuitable aromatic groups are phenyl, tolyl, xylyl and biphenyl.Non-limiting examples of suitable aliphatic groups include methyl,ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl,3-methylpentyl and 3,5,5-trimethylhexyl.

Another preferred group of cationogens includes substituted silyliumcationic compounds having the formula:

wherein R¹, R² and R³, are independently hydrogen, or a linear, branchedor cyclic aromatic or aliphatic group, with the proviso that only one ofR¹, R² and R³ may be hydrogen. Preferably, none of R¹, R² and R³ is H.Preferably, R¹, R² and R³ are, independently, a C₁ to C₂₀ aromatic oraliphatic group. More preferably, R¹, R² and R³ are independently a C₁to C₈ alkyl group. Examples of useful aromatic groups are phenyl, tolyl,xylyl and biphenyl. Non-limiting examples of useful aliphatic groupsinclude methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl,decyl, dodecyl, 3-methylpentyl and 3,5,5-trimethylhexyl. A preferredgroup of reactive substituted silylium cations includetrimethylsilylium, triethylsilylium and benzyldimethylsilylium. Suchcations may be prepared, for example, by the exchange of the hydridegroup of the R¹R²R³Si—H with a non-coordinating anion (NCA), such asPh₃C⁺B(pfp)₄ ⁻ yielding compositions such as R¹R²R³SiB(pfp)₄ which inthe appropriate solvent obtain the cation.

According to the present invention, Ab- denotes an anion. Preferredanions include those containing a single coordination complex possessinga charge bearing metal or metalloid core which is negatively charged tothe extent necessary to balance the charge on the active catalystspecies which may be formed when the two components are combined. Morepreferably Ab- corresponds to a compound with the general formula [MQ4]⁻wherein M is a boron, aluminum, gallium or indium in the +3 formaloxidation state; and Q is independently hydride, dialkylamido, halide,hydrocarbyl, hydrocarbyloxide, halo-substituted hydrocarbyl,halo-substituted hydrocarbyloxide, or halo-substituted silylhydrocarbylradicals.

Preferably, the monomer mixture to prepare the butyl polymer contains inthe range of from about 80% to about 99% by weight of at least oneisoolefin monomer and in the range of from about 1.0% to about 20% byweight of at least one multiolefin monomer and/or β-pinene. Morepreferably, the monomer mixture contains in the range of from 83% to 98%by weight of at least one isoolefin monomer and in the range of from2.0% to 17% by weight of a multiolefin monomer or β-pinene. Mostpreferably, the monomer mixture contains in the range of from 85% to 97%by weight of at least one isoolefin monomer and in the range of from3.0% to 15% by weight of at least one multiolefin monomer or β-pinene.

The monomers are generally polymerized cationically, preferably attemperatures in the range of from about −120° C. to about −50° C.,preferably in the range of from about −100° C. to about −70° C., morepreferably in a range of from about −98° C. to about −75° C., forexample about −98° C. to about −90° C. The operating temperatures ofabout −98° C. and about −75° C. are particularly noteworthy. Preferredpressures are in the range of from 0.1 to 4 bar.

The use of a continuous reactor as opposed to a batch reactor seems tohave a positive effect on the process. Preferably, the process isconducted in at least one continuous reactor having a volume of between0.1 m³ and 100 m³, more preferable between 1 m³ and 10 m³. Thecontinuous process is preferably performed with at least the followingfeed streams:

-   -   I) solvent/diluent comprising a tetraflourinated        propene+isoolefin (preferably isobutene)+multiolefin (preferably        diene, such as isoprene); and,    -   II) initiator system comprising a Lewis acid and proton source.

For economical production, a continuous process conducted in slurry(suspension) in a diluent is desirable, as described in U.S. Pat. No.5,417,930, the entire contents of which is herein incorporated byreference.

The diluent preferably comprises at least one hydrofluorinated olefincomprising at least three carbon atoms and at least three fluorineatoms, as described by Formula I:

C_(x)H_(y)F_(z)   (I)

wherein x is an integer with a value of 3 or greater, z is an integerwith a value of 3 or greater, and y+z is 2x. The value of x ispreferably from 3 to 6, more preferably from 3 to 5, yet more preferably3. The value of z is preferably from 3 to 8, more preferably from 4 to6, yet more preferably 4. Y is an integer with a value of 2x-z and maybe in the range of, for example 2 to 10, 3 to 9, 4 to 8 or 4 to 6. Thevalue of y is preferably 2.

Examples of suitable diluents having three or more carbon atoms andthree or more fluorine atoms include 1,1,2-trifluoropropene;1,1,3-trifluoropropene; 1,2,3-trifluoropropene; 1,3,3-trifluoropropene;2,3,3-trifluoropropene; 3,3,3-trifluoropropene;1,3,3,3-tetrafluoro-1-propene; 2,3,3,3-tetrafluoro-1-propene;1,1,3,3-tetrafluoro-1-propene, 1,1,2,3-tetrafluoro-1-propene,1,2,3,3-tetrafluoro-1-propene, 1,1,2,3-tetrafluoro-1-butene;1,1,2,4-tetrafluoro-1-butene; 1,1,3,3-tetrafluoro-1-butene;1,1,3,4-tetrafluoro-1-butene; 1,1,4,4-tetrafluoro-1-butene;1,2,3,3-tetrafluoro-1-butene; 1,2,3,4-tetrafluoro-1-butene;1,2,4,4-tetrafluoro-1-butene; 1,3,3,4-tetrafluoro-1-butene;1,3,4,4-tetrafluoro-1-butene; 1,4,4,4-tetrafluoro-1-butene;2,3,3,4-tetrafluoro-1-butene; 2,3,4,4-tetrafluoro-1-butene;2,4,4,4-tetrafluoro-1-butene; 3,3,4,4-tetrafluoro-1-butene;3,4,4,4-tetrafluoro-1-butene; 1,1,2,3,3-pentafluoro-1-butene;1,1,2,3,4-pentafluoro-1-butene; 1,1,2,4,4-pentafluoro-1-butene;1,1,3,3,4-pentafluoro-1-butene; 1,1,3,4,4-pentafluoro-1-butene;1,1,4,4,4-pentafluoro-1-butene; 1,2,3,3,4-pentafluoro-1-butene;1,2,3,4,4-pentafluoro-1-butene; 1,2,4,4,4-pentafluoro-1-butene;2,3,3,4,4-pentafluoro-1-butene; 2,3,4,4,4-pentafluoro-1-butene;3,3,4,4,4-pentafluoro-1-butene; 1,1,2,3,3,4-hexafluoro-1-butene;1,1,2,3,4,4-hexafluoro-1-butene; 1,1,2,4,4,4-hexafluoro-1-butene;1,2,3,3,4,4-hexafluoro-1-butene; 1,2,3,4,4,4-hexafluoro-1-butene;2,3,3,4,4,4-hexafluoro-1-butene; 1,1,2,3,3,4,4-heptafluoro-1-butene;1,1,2,3,4,4,4-heptafluoro-1-butene; 1,1,3,3,4,4,4-heptafluoro-1-butene;1,2,3,3,4,4,4-heptafluoro-1-butene; 1,1,1,2-tetrafluoro-2-butene;1,1,1,3-tetrafluoro-2-butene; 1,1,1,4-tetrafluoro-2-butene;1,1,2,3-tetrafluoro-2-butene; 1,1,2,4-tetrafluoro-2-butene;1,2,3,4-tetrafluoro-2-butene; 1,1,1,2,3-pentafluoro-2-butene;1,1,1,2,4-pentafluoro-2-butene; 1,1,1,3,4-pentafluoro-2-butene;1,1,1,4,4-pentafluoro-2-butene; 1,1,2,3,4-pentafluoro-2-butene;1,1,2,4,4-pentafluoro-2-butene; 1,1,1,2,3,4-hexafluoro-2-butene;1,1,1,2,4,4-hexafluoro-2-butene; 1,1,1,3,4,4-hexafluoro-2-butene;1,1,1,4,4,4-hexafluoro-2-butene; 1,1,2,3,4,4-hexafluoro-2-butene;1,1,1,2,3,4,4-heptafluoro-2-butene; 1,1,1,2,4,4,4-heptafluoro-2-butene;and mixtures thereof.

Examples of HFO's with four or more fluorine atoms and three or morecarbon atoms are 1,3,3,3-tetrafluoro-1-propene;2,3,3,3-tetrafluoro-1-propene; 1,1,3,3-tetrafluoro-1-propene,1,1,2,3-tetrafluoro-1-propene, 1,2,3,3-tetrafluoro-1-propene;1,1,2,3-tetrafluoro-1-butene; 1,1,2,4-tetrafluoro-1-butene;1,1,3,3-tetrafluoro-1-butene; 1,1,3,4-tetrafluoro-1-butene;1,1,4,4-tetrafluoro-1-butene; 1,2,3,3-tetrafluoro-1-butene;1,2,3,4-tetrafluoro-1-butene; 1,2,4,4-tetrafluoro-1-butene;1,3,3,4-tetrafluoro-1-butene; 1,3,4,4-tetrafluoro-1-butene;1,4,4,4-tetrafluoro-1-butene; 2,3,3,4-tetrafluoro-1-butene;2,3,4,4-tetrafluoro-1-butene; 2,4,4,4-tetrafluoro-1-butene;3,3,4,4-tetrafluoro-1-butene; 3,4,4,4-tetrafluoro-1-butene;1,1,2,3,3-pentafluoro-1-butene; 1,1,2,3,4-pentafluoro-1-butene;1,1,2,4,4-pentafluoro-1-butene; 1,1,3,3,4-pentafluoro-1-butene;1,1,3,4,4-pentafluoro-1-butene; 1,1,4,4,4-pentafluoro-1-butene;1,2,3,3,4-pentafluoro-1-butene; 1,2,3,4,4-pentafluoro-l-butene;1,2,4,4,4-pentafluoro-1-butene; 2,3,3,4,4-pentafluoro-1-butene;2,3,4,4,4-pentafluoro-1-butene; 3,3,4,4,4-pentafluoro-1-butene;1,1,2,3,3,4-hexafluoro-1-butene; 1,1,2,3,4,4-hexafluoro-1-butene;1,1,2,4,4,4-hexafluoro-1-butene; 1,2,3,3,4,4-hexafluoro-1-butene;1,2,3,4,4,4-hexafluoro-1-butene; 2,3,3,4,4,4-hexafluoro-1-butene;1,1,2,3,3,4,4-heptafluoro-1-butene; 1,1,2,3,4,4,4-heptafluoro-1-butene;1,1,3,3,4,4,4-heptafluoro-1-butene; 1,2,3,3,4,4,4-heptafluoro-1-butene;1,1,1,2-tetrafluoro-2-butene; 1,1,1,3-tetrafluoro-2-butene;1,1,1,4-tetrafluoro-2-butene; 1,1,2,3-tetrafluoro-2-butene;1,1,2,4-tetrafluoro-2-butene; 1,2,3,4-tetrafluoro-2-butene;1,1,1,2,3-pentafluoro-2-butene; 1,1,1,2,4-pentafluoro-2-butene;1,1,1,3,4-pentafluoro-2-butene; 1,1,1,4,4-pentafluoro-2-butene;1,1,2,3,4-pentafluoro-2-butene; 1,1,2,4,4-pentafluoro-2-butene;1,1,1,2,3,4-hexafluoro-2-butene; 1,1,1,2,4,4-hexafluoro-2-butene;1,1,1,3,4,4-hexafluoro-2-butene; 1,1,1,4,4,4-hexafluoro-2-butene;1,1,2,3,4,4-hexafluoro-2-butene; 1,1,1,2,3,4,4-heptafluoro-2-butene;1,1,1,2,4,4,4-heptafluoro-2-butene; and mixtures thereof.

Tetrafluorinated propenes having four fluorine atoms and three carbonatoms are of particular note. Examples are 1,3,3,3-tetrafluoro-1-propene(HFO-1234ze), 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf),1,1,3,3-tetrafluoro-1-propene, 1,1,2,3-tetrafluoro-1-propene,1,2,3,3-tetrafluoro-1-propene and mixtures thereof. Tetrafluorinatedpropenes can exist in either the Z or E isomeric forms or as a mixtureof Z and E isomeric forms. 1,3,3,3-tetrafluoro-1-propene (HFO-1234ze)and 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf) are especially preferred.HFO-1234yf (2,3,3,3-tetrafluoro-1-propene) is most preferred.

The diluent may also comprise one or more other inert solvents known tothe person skilled in the art for butyl polymerization. Such other inertsolvents may be, for example, halogenated hydrocarbons other thanhydrofluorocarbons (e.g. methyl chloride, dichloromethane or mixturesthereof).

EXAMPLES

All polymerizations were done in a dried, inert atmosphere. Thepolymerizations were performed as batch reactions in 600 mL stainlesssteel reaction vessels, equipped with an overhead 4-blade stainlesssteel impeller driven by an external electrically driven stirrer.Reaction temperature was measured via a thermocouple. The reactor wascooled to the desired reaction temperature, listed in the Tables, byimmersing the assembled reactor into a pentane cooling bath. Thetemperature of the stirred hydrocarbon bath was controlled to ±2° C. Allapparatus in liquid contact with the reaction medium were dried at 150°C. for at least 6 hours and cooled in a vacuum-nitrogen atmospherealternating chamber before use. High purity isobutene and methylchloride were received from LANXESS manufacturing facility and used asis. The hydrofluorocarbon 1,1,1,2-tetrafluoroethane (>99.9% purity)(HFC-134a, Genetron@ 134a) and hydrofluoroolefins(E)-1,3,3,3-tetrafluoro-1-propene (>99.99% purity) (HFO-1234ze,Solstice@ 1234ze Refrigeration Grade) and 2,3,3,3-tetrafluoro-1-propene(>99.99% purity) (HFO-1234yf, Solstice@ 1234yf Automotive Grade) werepurchased from Honeywell and were used as received. All were condensedand collected as liquids in the dry box. Isoprene (Sigma-Aldrich, >99.5%purity) was dried over activated 3A molecular sieves for several daysand distilled under nitrogen. A 1.0 M solution of ethylaluminumdichloride in hexanes (Sigma-Aldrich) was used as received. A solutionof HCl/CH₂Cl₂ was prepared by bubbling anhydrous HCl gas (Sigma-Aldrich,99% purity) through a pre-dried Sure/Seal™ bottle containing anhydrousCH₂Cl₂ (VWR). The HCl/CH₂Cl₂ solution was then titrated using 0.1 N NaOH(VWR) standard solution to determine its concentration.

The slurry polymerizations were performed by charging the monomer,comonomer and liquefied diluent (specified in each of the examples) intoa chilled reaction vessel at polymerization temperature and stirred at apredetermined stirring speed between 500 to 900 rpm. Theinitiator/coinitiator solutions were prepared in methyl chloride. Theinitiator/coinitiator solutions were prepared under the same temperatureconditions as the reaction vessel by diluting the HCl/CH₂Cl₂ solutioninto an aliquot of methyl chloride and adding the 1.0 M solution of theethylaluminum dichloride to a 1:4 molar ratio of HCl:EADC, followed bygentle swirling. The initiator/coinitiator solution was usedimmediately. The initiator/coinitiator solution was added to thepolymerization using a chilled glass Pasteur pipette. The reaction wasallowed to run for 5 minutes and stopped by the addition of 2 mL of a 1%sodium hydroxide in ethanol solution. Conversion is reported as weightpercent of the monomers converted to polymer at the polymerizationtemperature.

The molecular weight of the polymers was determined by GPC (gelpermeation chromatography) using a Waters 2690/5 Separations Module anda Waters 2414 Refractive Index Detector. Tetrahydrofuran was used aseluent (0.8 mL/min, 35° C.) with a series of three Agilent PL gel 10 μmMixed-B LS 300×5.7 mm columns.

Isoprene incorporation was determined by ¹H-NMR spectrometry. NMRmeasurements were obtained using a Bruker DRX 500 MHz spectrometer(500.13 MHz) using CDCl₃ solutions of polymers with the residual CHCl₃peak used as an internal reference.

Oligomer level determination was performed by GC-FID using an Agilent6890 Series Plus using an Agilent J+W VF-1 ms 30×0.25 (1.0) column(inlet 275° C., 22.5 psi) and an FID temperature of 300° C. equippedwith a HP 7683 Series auto injector.

Example A Polymerizations with Pure Diluents at −95° C.

Table 1 lists the results of polymerizations conducted at −95° C. inmethyl chloride (Examples 1 and 2), HFO-1234ze (Examples 3 and 4),HFO-1234yf (Examples 5 and 6) and HFC-134a (Examples 7 and 8). Allpolymerizations were performed consistently as reported above in a 600mL stainless steel vessel using HCl/EADC as the initiator/coinitiator.Polymerizations were run with 180 mL diluent, 20 mL of isobutene and 0.6mL of isoprene (isoprene content in feed=2.3 mol %). Theinitiator/coinitiator solution was prepared in 40 mL MeCl using 6 mL ofa 0.16 M HCl/CH₂Cl₂ solutions and 4 mL of a 1.0 M hexane solution ofethylaluminum dichloride (EADC). The same volume ofinitiator/coinitiator solution (5 ml) was used in all examples in Table1, which also provides more details on oligomer composition in eachexample.

TABLE 1 Total Vol Yield Conversion Mw Unsats¹⁾ Oligomers C21/C13 Ex.Diluent (%) (g) (Wt. %) ×10³ Mw/Mn (mol %) (ppm) Ratio 1 CH₃Cl 100 13.286 538 5.2 1.78 9274 1.18 2 CH₃Cl 100 13.9 94 595 5 1.75 7436 1.09 3HFO- 100 4.4 30 477 6.3 2.03 1094 3.64 1234ze 4 HFO- 100 4.6 31 465 6.12.12 865 2.95 1234ze 5 HFO- 100 12.1 82 445 3.6 2.24 637 1.47 1234yf 6HFO- 100 12.4 84 479 3.6 2.26 632 1.32 1234yf 7 HFC- 100 4.7 31 266 6.51.69 3004 8.19 134a 8 HFC- 100 5.4 37 280 6.7 1.83 2726 7.11 134a¹⁾Total unsats = 1,4-isoprene + isoprenoid.

With reference to FIG. 1A, polymerization in HFO-1234yf shows anexcellent temperature profile with a moderate temperature spike andextended reaction time in comparison to polymerizations in methylchloride (MeCl).

Polymerizations using MeCl resulted in significant fouling around wallsof the reaction vessel, temperature probe and stirring shaft as well asrubber ball formation in the reaction medium. Polymerizations using bothhydrofluorocarbon and hydrofluoroolefins resulted in minimal or nofouling on the reaction vessel, temperature probe and stirring shaft.The HFO-1234yf produced a very stable, uniform rubber slurry with nopolymer agglomeration.

Under the same reaction conditions at −95° C. reaction temperature, thepolymerization reactivity in HFO-1234yf is excellent (av. 83%conversion) and is quite comparable albeit slightly lower than that ofthe conventional diluent methyl chloride (av. 90% conversion). However,the results show a marked difference in polymerization reactivity forhydrofluorocarbon HFC-134a vs hydrofluoroolefin HFO-1234yf. Thereactions done in HFO-1234yf (av. 83% conversion) give much higherpolymer yield than that of HFC-134a (av. 34% conversion). Thehydrofluorolefin isomer (E) HFO-1234ze shows polymerization reactivity(av. 30% conversion) similar to that of HFC-134a.

In addition to the high polymer conversions, the butyl polymer samplesobtained from HFO-1234yf diluent give the best combination of propertiessuch as high molecular weight, narrow molecular weight distribution,high isoprene incorporation and low levels of the cylic oligomerby-products (Table 1). It is clearly seen that rubber produced usingHFO-1234yf as diluent have significantly higher weight-average molecularweight (M_(w)) than that produced in HFC-134A, similar M_(w) to thatproduced in HFO-1234ze and lower M_(w) to that produced in MeCl. Whencomparing the average of duplicate reactions, the M_(w) achieved forHFO-1234yf polymerizations performed at −95° C. (Ex. 5 & 6) was 462,000compared to averages of 567,000 for MeCl (Ex. 1 & 2), 273,000 forHFC-134A (Ex. 7 & 8) and 471,000 for HFO1234ze (Ex. 3 & 4).

It is well known that cyclic oligomers namely C₁₃H₂₄ and C₂₁H₄₀compounds are inherently formed as by-products during butylpolymerization process. The molecular structures of these cyclicoligomers are shown below in Scheme 1 where the C₁₃H₂₄ isomer contains 1molecule of isoprene and 2 molecules of isobutylene and the C₂₁H₄₀isomer contains 1 molecule of isoprene and 4 molecules of isobutylene.These cyclic oligomers exist in trace amounts in regular butyl finishedproducts. The presence of C₁₃H₂₄ and C₂₁H₄₀ in butyl rubber is ofcurrent concern in the pharmaceutical application. These species are themajor extractables in certain pharma rubber closure formulations.

In addition to providing surprisingly low levels of oligomers, use oftetraflourinated propene diluents also resulted in a surprisinglyfavourable ratio of C21/C13 oligomers. For example, use of HFO-1234yfprovided ratios of 1.32 and 1.47, whereas use of HFC-134a providedratios of 7.11 and 8.19. Since the lower molecular weight C13 oligomersare preferentially removed during steam stripping and rubber dryingoperations, a low ratio is advantageous in that a finished product canbe made with even lower levels of total oligomers.

While HFO-1234ze diluent tends to give lower copolymer conversions, thebutyl polymer samples produced from this diluent shows excellentproperties in terms of molecular weight, isoprene incorporation andcylic oligomers content. Overall, both tetrafluorinated propenes,HFO-1234yf and HFO-1234ze, show better behavior and are more suitablefor butyl slurry polymerization than HFC-134a at low temperatures.

Although the NMR data is not presented here, overall it was found thatlower polymer branching occurred when HFO-1234yf diluents were used,while HFO-1234ze diluents produced polymers with similar branching toHFC-134a diluents.

Example B Polymerizations with Pure Diluents at −75° C.

Table 2 lists the results of polymerizations conducted at −75° C. inmethyl chloride (Examples 9 and 10), HFO-1234ze (Examples 11 and 12),HFO-1234yf (Examples 13 and 14) and HFC-134a (Examples 15 and 16). Allpolymerizations were performed consistently as reported above in a 600mL stainless steel vessel using HCl/EADC and the initiator/coinitiator.Polymerizations were run with 180 mL diluent, 20 mL of isobutene and 0.6mL of isoprene (isoprene content in feed=2.3 mol %). Theinitiator/coinitiator solution was prepared in 40 mL MeCl using 6 mL ofa 0.16 M HCl/CH₂Cl₂ solutions and 4 mL of a 1.0 M hexane solution ofethylaluminum dichloride (EADC). The same volume ofinitiator/coinitiator solution (5 mL) was used for all polymerizations.

TABLE 2 Total Vol Yield Conversion Mw Unsats¹⁾ Oligomers C21/C13 Ex.Diluent (%) (g) (Wt. %) ×10³ Mw/Mn (mol %) (ppm) Ratio 9 CH₃Cl 100 13.692 294 5.11 1.44 22522 1.94 10 CH₃Cl 100 13.7 93 344 5.51 1.44 223161.90 11 HFO- 100 1.6 11 220 8.00 1.68 12774 6.77 1234ze 12 HFO- 100 1.510 212 9.45 1.68 15443 6.34 1234ze 13 HFO- 100 12.2 83 331 3.79 2.124321 1.39 1234yf 14 HFO- 100 13 88 410 3.83 2.09 3036 1.24 1234yf 15HFC- 100 13 88 267 3.79 1.95 3392 1.57 134a 16 HFC- 100 13.2 89 222 3.832.05 4905 1.75 134a ¹⁾Total unsats = 1,4-isoprene + isoprenoid.

At a higher reaction temperature of −75° C., the polymerization becomesmuch more reactive in HFC-134a, the conversion levels (av. 89%conversion) are now comparable to that of HFO-1234yf (av. 85%conversion). The experiments carried out in HFC-134a and HFO-1234yfshows comparable reactivity; however both of these diluents showslightly lower reaction conversions than the conventional diluent methylchloride. The temperature has no impact on the HFO-1234ze as thisdiluent still exhibits poor reactivity despite a higher reactiontemperature.

At the higher polymerization temperature the polymer produced inHFO-1234yf possessed the highest Mw. When comparing the averages forduplicate polymerizations performed at −75° C. HFO-1234yf (Ex. 13 & 14)produced polymer with Mw=371,000, HFC-134A (Ex. 15 & 16) Mw=245,000,HFO-1234ze (Ex. 11 & 12) Mw=216,000 and MeCl (Ex. 9 & 10) Mw=319,000.This is an important advantage for a continuous butyl productionprocess, as a high Mw and related desirable physical properties can bemaintained in the product even at higher reactor temperatures.

Comparing the data shown in Tables 1 and 2, the overall impact of higherreaction temperature is the reduction in the polymer chain molecularweights (Mw) and a significant increase in the cyclic oligomers content.The effects follow the same trends for all diluents, however the butylpolymer samples produced from HFO-1234yf maintain higher polymermolecular weights relative to HFC-134a. The total unsaturation level isslightly higher for HFO-1234yf (av. 2.1 mol %) vs. HFC-134a (av. 2.0 mol%), whereas the cyclic oligomer level is lower for HFO-1234yf (av. 3679ppm) vs. HFC-134a (av. 4148 ppm). The ratio of C21/C13 is morefavourable with HFO-1234yf than with HFC-134a. Similarly, observationscan be made comparing HFO-1234yf vs. methyl chloride with regard to thecopolymer molecular weights.

The total unsaturation level and therefore the isoprene level is muchhigher in butyl polymer samples produced in HFO-1234yf vs. methylchloride. As seen in Tables 1 and 2, rubber produced using HFO-1234yf asdiluent contains significantly more unsaturation from incorporatedisoprene than compared to the other diluents when using an equalconcentration of isoprene in the mixed feed for the reaction. Whencomparing the average of duplicate reactions, the total unsaturationachieved for HFO-1234yf polymerizations performed at −95° C. (Ex. 5 & 6)was 2.25 mol % compared to averages of 1.77 mol % for MeCl (Ex. 1 & 2),1.76 mol % for HFC-134A (Ex. 7 & 8) and 2.08 mol % for HFO-1234ze (Ex. 3& 4). Isoprene incorporation for HFC-134A is limited at −95° C. due tolow conversions at this temperature. The same trends exist whencomparing the averages for duplicate polymerizations performed at hightemperature (−75° C.), with HFO-1234yf (Ex. 13 & 14) incorporating onaverage 2.11 mol % total isoprene, HFC-134A (Ex. 15 & 16) 2.00 mol %,HFO-1234ze (Ex. 11 & 12) 1.68 mol % and MeCl (Ex. 9 & 10) 1.44 mol %.Isoprene incorporation for HFO-1234ze is limited at −75° C. due to lowconversions at this temperature. The improved incorporation of isopreneinto the butyl rubber results in a lower concentration of isoprenerequired in the feed stream to reach equivalent unsaturation levels inthe finished product, resulting in cost savings for a continuous slurrymanufacturing process. In addition, the cyclic oligomer levels arenotably higher in methyl chloride vs. HFO-1234yf and HFC-134a and theC21/C13 ratios are also undesirably higher. Overall, the polymerizationbehavior and the advantages of HFO-1234yf are applicable under differentreaction temperatures, i.e. at −95° C. and −75° C.

Example C Polymerizations with 50:50 Mixtures of Diluents at −95° C.

Table 3 lists the results of polymerizations conducted at −95° C. in50:50 mixture of MeCl:HFO-1234ze (Examples 17 and 18) and 50:50 mixtureof MeCl:HFO-1234yf (Examples 19 and 20). All polymerizations wereperformed consistently as reported above in a 600 mL stainless steelvessel using HCl/EADC and the initiator/coinitiator. Polymerizationswere run with 180 mL diluent, 20 mL of isobutene and 0.6 mL of isoprene(isoprene content in feed=2.3 mol %). The initiator/coinitiator solutionwas prepared in 40 mL MeCl using 6 mL of a 0.16 M HCl/CH₂Cl₂ solutionsand 4 mL of a 1.0 M hexane solution of ethylaluminum dichloride (EADC).The same volume of initiator/coinitiator solution (5 mL) was used forall polymerizations.

TABLE 3 Total Vol Yield Conversion Mw Unsats¹⁾ Oligomers C21/C13 Ex.Diluent (%) (g) (Wt. %) ×10³ Mw/Mn (mol %) (ppm) Ratio 17 CH₃Cl/ 50/504.8 33 243 4.18 1.39 5489 2.77 HFO- 1234ze 18 CH₃Cl/ 50/50 6.1 42 2384.13 1.46 4621 2.25 HFO- 1234ze 19 CH₃Cl/ 50/50 11.1 75 458 4.61 1.743334 1.52 HFO- 1234yf 20 CH₃Cl/ 50/50 9.1 62 455 5.02 1.62 3509 1.90HFO- 1234yf ¹⁾Total unsats = 1,4-isoprene + isoprenoid.At −95° C. reaction temperature, the polymerizations using mixtures ofdiluent produced, in general, similar trends as those observed in purediluent. Thus, the reactions in the 50:50 blend of methylchloride/HFO-1234yf (av. 68% conversion) are more reactive than theblends of methyl chloride/HFO-1234ze (av. 38% conversion). The butylpolymer samples obtained from methyl chloride/HFO-1234yf also exhibithigher molecular weights and higher isoprene incorporation than in themethyl chloride/HFO-1234ze diluent mixture. The cyclic oligomer levelsare lower for methyl chloride/HFO-1234yf than in the case of methylchloride/HFO-1234ze. Additionally, the ratio of C21/C13 is lower formethyl chloride/HFO-1234yf compared to the methylchloride/HFO-1234ze-containing diluent mixture.

The butyl rubber produced in a MeCl blend with HFO-1234yf possessedsignificantly higher Mw than in HFO-1234ze. When comparing the averagesfor duplicate polymerizations performed at −95° C. blends of MeCl withHFO1234yf (Ex. 19 & 20) produced polymer with Mw=457,000 while HFO1234ze(Ex. 17 & 18) produced polymer with Mw=241,000. This is an importantadvantage for the continuous slurry process for butyl rubber production.A high Mw can be maintained even with a blend of HFO-1234yf with MeCl,resulting in lower operating costs compared to 100% HFO-1234yf withoutloss of other advantages of the fluorinated diluent system. Minimal tono fouling was observed on the surfaces in contact with the reactionmixtures for all cases. In comparison, the polymerization in methylchloride resulted in a heavy coating of polymer on the reactor walls,temperature probe and stirring shaft as well as large amounts polymeragglomerate in the reaction medium.

Example D Polymerizations with 50:50 Mixtures of Diluents at −75° C.

Table 4 lists the results of polymerizations conducted at −75° C. in a50:50 mixture of MeCl:HFO-1234ze (Examples 21 and 22) and 50:50 mixtureof MeCl:HFO-1234yf (Examples 23 and 24). All polymerizations wereperformed consistently as reported above in a 600 mL stainless steelvessel using HCl/EADC and the initiator/coinitiator. Polymerizationswere run with 180 mL diluent, 20 mL of isobutene and 0.6 mL of isoprene(isoprene content in feed=2.3 mol %). The initiator/coinitiator solutionwas prepared in 61 mL MeCl using 11 mL of a 0.18 M HCl/CH₂Cl₂ solutionsand 8 mL of a 1.0 M hexane solution of ethylaluminum dichloride (EADC).The same volume of initiator/coinitiator solution (5 mL) was used forall polymerizations.

TABLE 4 Total Vol Yield Conversion Mw Unsats¹⁾ Oligomers C21/C13 Ex.Diluent (%) (g) (Wt. %) ×10³ Mw/Mn (mol %) (ppm) Ratio 21 CH₃Cl/ 50/503.6 25 145 4.18 1.2 15925 5.06 HFO- 1234ze 22 CH₃Cl/ 50/50 1.8 12 1061.83 1.08 18877 6.20 HFO- 1234ze 23 CH₃Cl/ 50/50 13.0 88 310 4.89 1.4519588 2.35 HFO- 1234yf 24 CH₃Cl/ 50/50 13.1 89 275 5.18 1.42 21730 2.36HFO- 1234yf ¹⁾Total unsats = 1,4-isoprene + isoprenoid.The polymerizations using a mixture of diluents at −75° C. producedsignificant fouling for all mixtures of diluent. MeCl/HFO-1234ze mixtureresulted in a polymer solely fouled around the stirring shaft, whileMeCl/HFO-1234yf resulted in the heavy fouling on the stirring shaftalong with the formation of rubber balls in the reaction medium. Incomparison, the polymerization in methyl chloride resulted in a heavycoating of polymer on the reactor walls, temperature probe and stirringshaft as well as large amounts of polymer agglomerate in the reactionmedium.

Again in this case, the temperature has relatively little impact onpolymer conversions for the reactions involving methylchloride/HFO-1234ze. The highest conversions and molecular weights wereobtained with methyl chloride/HFO-1234yf.

The butyl rubber produced in a blend with HFO-1234yf possessed higher Mwthan in HFO-1234ze. When comparing the averages for duplicatepolymerizations performed at −75° C. blends of MeCl with HFO-1234yf (Ex.21 & 22) produced polymer with Mw=457,000 while HFO-1234ze (Ex. 23 & 24)produced polymer with Mw=241,000. This is an important advantage for thecontinuous slurry process for butyl rubber production, proving that highMw is maintained even at higher polymerization temperatures with a blendof HFO-1234yf in MeCl.

Example E Effect of Steam Stripping on Polymers to Reduce C13 CyclicOligomer Content

For polymers produced according to selected experimental conditions,steam stripping was performed as a finishing step to reduce the C13cyclic oligomer content and thereby reduce the total extractable cyclicoligomers from the polymer. This finishing step takes advantage of thefavourably low ratio of C21/C13 observed for polymers produced using theHFO's of the present invention in order to produce polymers withdesirable reduced total oligomer content.

For each sample, 2 g of polymer (that had been previously coagulated inethanol and evaporated at room temperature) was dissolved in 20 mL ofhexane. It should be noted that the ethanol coagulation step resulted insome extraction of cyclic oligomers; this resulted in lower initialtotal oligomer levels and a higher ratio of C21/C13 for these samplesthan reported above. The hexane solvent dissolved the C13 oligomers fromthe sample and the solvent was removed, along with the oligomers, bysteam stripping for thirty minutes. The polymer was recovered andre-dissolved in hexane for subsequent oligomer analysis by GC/MS.Results of the analysis are provided in Table 5.

TABLE 5 Total C21/C13 Total C21/C13 oligomer ratio oligomer ratio (ppm)before before (ppm) after after Ex. Diluent stripping strippingstripping stripping 5 HFO-1234yf 165 3.7 124 7.2 @ −95° C. 8 HFC-134a242 7.9 209 16.4 @ −95° C. 14 HFO-1234yf 242 4.1 213 7.9 @ −75° C. 16HFC-134a 417 6.3 346 10.89 @ −75° C.

By utilizing steam stripping as a finishing process, it was possible toproduce polymers with a low total oligomer content from polymers createdusing the HFO diluent. As can be seen from Table 5, steam strippingreduced the total oligomer content of the samples produced usingHFO-1234yf diluent to a lower level than those produced using HFC-134adiluent. Although a reduction in cyclic oligomer levels was observed forpolymers produced at all temperatures, it was most pronounced for thoseproduced at the lower temperature of −95° C., since the ratio of C21/C13was favourable for HFO diluents at that temperature. The lowest overallcyclic oligomer levels were obtained with polymer produced usingHFO-1234yf at −95° C. Using the steam stripping process, a butyl polymerwith total cyclic oligomers of less than 125 ppm was produced. Since theC13 was extracted, in all cases the ratio of C21/C13 increased followingsteam stripping. The polymers produced using the steam strippingfinishing process are novel in that they possess the highest purity andlowest overall level of total cyclic oligomers, which is advantageous inpharmaceutical applications.

Series of polymerizations were performed in methyl chloride (MeCl),HFC-134A and HFO1234yf as diluents at various isoprene contents in thereaction feed. The polymerizations were conducted as describedpreviously except 1.5 mL of isoprene was used in the feed for the highisoprene polymerizations (isoprene content in feed=5.6 mol %). Theoligomer content was measured for samples of polymer taken directly fromthe reaction vessel or after steam stripping the reaction mixture inorder to mimic conditions in a plant production process. Results areshown in Table 6.

TABLE 6 Isoprene Content Total Total in Feed Unsats¹⁾ Conversion SampleC13 C21 Oligomers²⁾ C21/C13 Ex. Diluent (mol %) (mol %) (Wt %) Prep²⁾(ppm) (ppm) (ppm) Ratio 25 CH₃Cl 2.3 1.42 49 Direct 1493 3585 5078 2.4Steam 1101 3490 4591 3.2 26 CH₃Cl 5.6 6.63 71 Direct 7237 7612 14849 1.1Steam 5092 6824 11916 1.3 27 HFC-134A 2.3 1.84 58 Direct 367 2263 26306.2 Steam 192 1874 2066 9.8 28 HFC-134A 5.6 4.98 81 Direct 1202 14652667 1.2 Steam 694 1326 2021 1.9 29 HFO-1234yf 2.3 2.22 65 Direct 254368 622 1.4 Steam 143 329 472 2.3 30 HFO-1234yf 5.6 6.14 38 Direct 8331152 1986 1.4 Steam 538 1075 1614 2.0 ¹⁾Total unsats = 1,4-isoprene +isoprenoid. ²⁾Oligomers measured on samples directly from polys reactoror after steam stripping.

As seen in Table 6, the use of HFO1234yf as a diluent for polymerizationresults in butyl rubber with significantly lower amounts of cyclicoligomers as compared to MeCl and HFC-134A. The oligomer levels measuredfor the samples removed directly from the polymerization are a truemeasure of the total oligomers formed during the reaction. The oligomerdata presented in Table 6 for samples removed directly from thepolymerization show the same trends as that observed in the data inTable 5. It is clearly seen that rubber produced using HFO1234yf (Ex.29) as diluent contains significantly less total oligomer than thatproduced in MeCl (Ex. 25) or HFC-134A (Ex. 27). FIG. 2 compares thetotal oligomer content for reactions performed with standard isoprenelevels (Examples 25, 27 and 29). The steam stripping purification stepwas performed in order to estimate the product purification occurring ina continuous butyl rubber manufacturing process. The steam strippingstep is observed to decrease the C13 content more preferentially forbutyl rubber produced in all diluents at similar rates. This is expectedas the C13 oligomers are known to be steam stripped during the finishingprocess.

As further seen in Table 6, the use of HFO1234yf as a diluent forpolymerization results in butyl rubber with significantly lower amountsof cyclic oligomers as compared to MeCl and HFC-134A at higher levels ofisoprene incorporation. Polymerizations were performed in the presenceof increased feed concentrations of isoprene with the various diluentsin order to produce butyl rubber with a high incorporated isoprenecontent. Similar to that observed for reactions performed at standardisoprene levels, a low oligomer content was achieved in the diluentHFO-1234yf (Ex. 30) as compared to MeCl (Ex. 26) or HFC-134A (Ex. 28).FIG. 3 compares the total oligomer content for high-isoprene feedcontent reactions. Following steam stripping, the polymer formed inHFO-1234yf diluent with high isoprene incorporation containedsignificantly lower oligomer than that measured for purified polymerprepared in HFC-134A and MeCl.

As seen in Table 7 and FIG. 4, the use of HFO-1234yf as a diluent inpolymerization reactions results in lower C21/C13 oligomer ratio ascompared to HFC-134A in the range of isoprene contents from 0-8 mol %.Polymerizations were performed with various ratios of isoprene in themonomer feed as listed in Table 7 (Examples 31-42), and the ratio of C21to C13 oligomers measured for polymer sampled directly out of thereactor is compared for polymerizations performed with feed isopreneconcentrations varying from 2.3 to 8.6 mol % in FIG. 4. A lower C21/C13ratio is observed for butyl produced in HFO-1234yf as compared toHFC-134A at all levels of isoprene. The C21/C13 ratio is observed to bequite similar for HFO-1234yf materials as compared to reactionsperformed in MeCl. It is known that the C13 oligomers are preferentiallyremoved during rubber separation and drying processes in the continuousmanufacturing process of butyl rubber. Therefore, a low C21/C13 ratio isdesirable for butyl rubber sampled directly out of the polymerizationreactor to yield finished product butyl rubber with low total oligomercontent.

TABLE 7 Isoprene Total Total Content Unsats¹⁾ Conversion C13 C21Oligomers²⁾ C21/C13 Ex. Diluent in Feed (mol %) (%) (ppm) (ppm) (ppm)Ratio 31 CH₃Cl 2.3 1.3 51 1915 5696 7611 3.0 32 4.5 2.5 40 2829 71489977 2.5 33 6.6 3.9 39 3549 6509 10058 1.8 34 8.6 5.1 38 4196 5744 99401.4 35 HFC- 2.3 2.0 31 311 2116 2427 6.8 36 134A 4.5 3.9 30 486 24192905 5.0 37 5.6 4.8 31 582 2355 2937 4.1 38 8.6 7.8 77 959 1601 2559 1.739 HFO- 2.3 1.9 29 417 1408 1825 3.4 40 1234yf 3.4 3.0 22 646 2099 27143.2 41 4.5 4.0 13 848 2659 3507 3.1 42 5.6 4.9 14 1855 4446 6301 2.4¹⁾Total unsats = 1,4-isoprene + isoprenoid ²⁾Oligomers measured onsamples directly from polys reactor or after steam stripping.

Example F Decreased Isoprenoid Content in Butyl Rubber

Butyl rubbers produced in Examples 1-16 were analyzed in order todetermine the effect of diluent on isoprenoid (short chain branching)content of the butyl copolymer. The results are provided in Table 8.Examples 1-16 are the same as in Tables 1 and 2 above.

TABLE 8 Reaction Total Isoprenoid Vol Temp Conversion Unsats¹⁾ Content²⁾Ex. Diluent (%) (° C.) (Wt. %) (mol %) (%) 1 MeCl 100 −95 86 1.78 15 2MeCl 100 −95 94 1.75 14 3 HFO-1234ze 100 −95 30 2.03 8 4 HFO-1234ze 100−95 31 2.12 8 5 HFO-1234yf 100 −95 82 2.24 5 6 HFO-1234yf 100 −95 842.26 5 7 HFC-134a 100 −95 31 1.69 10 8 HFC-134a 100 −95 37 1.83 10 9MeCl 100 −75 92 1.44 24 10 MeCl 100 −75 93 1.44 23 11 HFO-1234ze 100 −7511 1.68 19 12 HFO-1234ze 100 −75 10 1.68 18 13 HFO-1234yf 100 −75 832.12 9 14 HFO-1234yf 100 −75 88 2.09 8 15 HFC-134a 100 −75 88 1.95 11 16HFC-134a 100 −75 89 2.05 12 ¹⁾Total unsaturations = 1,4-isoprene (mol%) + isoprenoid (mol %). ²⁾Isoprenoid Content = Isoprenoid (mol %)/TotalUnsats (mol %).

As seen in table 8, rubber produced using 100% HFO-1234yf, HFC-134A orHFO-1234ze as diluent contain a lower measured isoprenoid content (shortchain branching) compared to MeCl when using an equal concentration ofisoprene in the mixed feed for the reaction. More significantly, it isseen when comparing the average of duplicate reactions thatpolymerizations in HFO-1234yf result in greatly reduced isoprenoidcontents at −95° C. The isoprenoid content for polymer produced inHFO-1234yf at −95° C. (Ex. 5 & 6) was 5.0% compared to averages of 15%for MeCl (Ex. 1 & 2), 10% for HFC-134A (Ex. 7 & 8) and 8% for HFO-1234ze(Ex. 3 & 4). This is significant since a butyl copolymer with a lowerisoprenoid content will have a higher proportion of total unsaturationsavailable in a 1,4-unit orientation for further chemical modification,and is expected to have higher efficiency in subsequent halogenationreactions in order to produce halobutyl rubber.

Short chain branches arise from back-biting reactions of a reactivechain end onto itself to form 5 carbon side chains attached to a smallproportion of the 1,4-isoprene units along the main chain. Thesesubstituted 1,4-isoprene units are referred to as isoprenoid unitsthroughout this document. The proportion of these units is significantfor the production of halobutyl rubber, since the substituted isoprenoidis not available for chemical modification by halogenation. As observedin Table 8, under standard butyl polymerization conditions using MeCl asdiluent, the isoprenoid content of the butyl produced is 15%. Therefore,under these standard conditions only 85% of the added isoprene units arein the 1,4-unit configuration and available to participate in furtherpolymer modification reactions such as halogenation. Therefore, it isexpected that a halogenation process will proceed to higher efficiencywith a butyl copolymer containing lower isoprenoid content, an importantfactor for the continuous production process of halobutyl rubber.

The same trends exist when comparing the averages for duplicatepolymerizations performed at high temperature (−75° C.), with materialprepared in HFO-1234yf (Ex. 13 & 14) containing on average 9.0%isoprenoid, HFC-134A (Ex. 15 & 16) 12%, HFO-1234ze (Ex. 11 & 12) 19% andMeCl (Ex. 9 & 10) 24%. This demonstrates that also at highertemperatures polymerizations performed in HFO-1234yf or HFC-134A producebutyl rubber containing significantly less short chain branching, andwould be expected to undergo halogenation more efficiently thanmaterials prepared in the other diluent systems.

A polymerization series was performed in pure diluents with a highcontent of isoprene in the reaction feed in order to prepare highisoprene butyl rubber. Table 9 lists the results of polymerizationsconducted in pure diluents at −95° C. with either standard isoprenemolar ratio in the feed (2.3 mol %) or high isoprene (5.6 mol %).

TABLE 9 Isoprene Iso- Content Con- Total prenoid in Feed version Mw Mw/Unsats¹⁾ Content²⁾ Ex. Diluent (mol %) (Wt. %) ×10³ Mn (mol %) (%) 1MeCl 2.3 86 538 5.2 1.78 15 2 MeCl 2.3 94 595 5 1.75 14 43 MeCl 5.6 70235 3.71 3.49 12 44 MeCl 5.6 71 246 4.13 3.42 12 45 HFC- 2.3 50 263 5.041.66 10 134A 46 HFC- 2.3 58 278 5.30 1.63 9 134a 47 HFC- 5.6 54 170 3.925.00 7 134a 48 HFC- 5.6 52 172 3.85 4.92 8 134a 49 HFO- 2.3 87 413 4.561.99 6 1234yf 50 HFO- 2.3 83 447 4.07 1.97 6 1234yf 51 HFO- 5.6 47 2404.07 5.40 6 1234yf 52 HFO- 5.6 47 261 4.30 5.11 5 1234yf ¹⁾Totalunsaturations = 1,4-isoprene (mol %) + isoprenoid (mol %). ²⁾IsoprenoidContent = Isoprenoid (mol %)/Total Unsats (mol %).

As seen in Table 9, rubber produced at −95° C. using HFO-1234yf asdiluent (Ex. 49 & 50) or HFC-134A (Ex. 45 & 46) contains lowerisoprenoid content than MeCl (Ex. 1 & 2) at standard isoprene ratio inthe mixed feed (2.3 mol %). Also, rubber produced using HFO-1234yf asdiluent (Ex. 49 & 50) contains lower isoprenoid content than HFC-134A(Ex. 45 & 46). More significantly, the trend is consistent at highisoprene feed ratio (5.6 mol %), where HFO-1234yf and HFC-134A resultedin an average isoprenoid content of 6% (Ex. 51 & 52) and 8% (Ex. 47 &48), respectively, as compared to 12% (Ex. 43 & 44) for MeCl. Similar toreactions performed at standard isoprene levels, the high isoprene butylrubber produced in HFO-1234yf contained significantly lower isoprenoidcontent compared to polymerizations performed in HFC-134A.

Polymerizations were also performed in blends of fluorinated solventwith MeCl as diluent. A series of polymerizations was performed usingvarious blend ratios of HFO-1234yf with MeCl under standard conditionsat −95° C., resulting in butyl with decreased isoprenoid content at allblend ratios as compared to 100% MeCl. Table 10 lists the results ofpolymerizations conducted in various blend ratios of HFO-1234yf withMeCl at −95° C.

TABLE 10 Total Isoprenoid Vol Conversion Mw Unsats¹⁾ Content²⁾ Ex.Diluent Blend (%) (Wt. %) ×10³ Mw/Mn (mol %) (%) 1 MeCl 100 86 538 5.21.78 15 2 MeCl 100 94 595 5 1.75 14 53 MeCl/HFO-1234yf 75/25 84 745 2.991.66 9 54 MeCl/HFO-1234yf 75/25 84 694 3.10 1.79 10 55 MeCl/HFO-1234yf50/50 86 673 2.67 1.67 8 56 MeCl/HFO-1234yf 50/50 82 691 2.75 1.67 8 57MeCl/HFO-1234yf 25/75 81 502 2.63 2.29 7 58 MeCl/HFO-1234yf 25/75 73 5272.54 2.30 6 59 HFO-1234yf 100 77 502 2.45 2.61 4 60 HFO-1234yf 100 74512 2.43 2.61 4 ¹⁾Total unsaturations = 1,4-isoprene (mol %) +isoprenoid (mol %). ²⁾Isoprenoid Content = Isoprenoid (mol %)/TotalUnsats (mol %).

As seen in Table 10, significantly lower isoprenoid content is obtainedin all blend ratios of MeCl with HFO-1234yf as compared to 100% MeCl.

Additionally, a polymerization series was performed using 50/50 blendsof MeCl with HFO-1234yf as diluent at temperatures ranging from −75° C.to −95° C. The isoprene content of the feed was 2.3 mol %. Table 11lists the results of polymerizations conducted in 50/50 ratio blends ofMeCl with HFO-1234yf at temperatures ranging from −75° C. to −95° C. Asseen in Table 11, across a range of temperatures the polymerizationsperformed in 50/50 blends of HFO-1234yf with MeCl produced butyl withlower isoprenoid content due to short chain branching from polymerbackbiting reactions.

TABLE 11 Reaction Total Isoprenoid MeCl/Diluent Temp Conversion MwUnsats¹⁾ Content²⁾ Ex. Blend (° C.) (Wt. %) ×10³ Mw/Mn (mol %) (%) 61HFO-1234yf −75 82 254 2.91 1.48 18 62 HFO-1234yf −75 85 265 2.99 1.45 1763 HFO-1234yf −80 82 229 3.07 1.47 20 64 HFO-1234yf −80 77 222 3.03 1.5320 65 HFO-1234yf −85 74 305 3.06 1.58 15 66 HFO-1234yf −85 73 300 2.891.65 15 67 HFO-1234yf −90 69 354 3.01 1.50 12 68 HFO-1234yf −90 77 3482.94 1.60 13 69 HFO-1234yf −95 48 285 3.08 1.57 11 70 HFO-1234yf −95 47300 2.90 1.51 11 ¹⁾Total unsaturations = 1,4-isoprene (mol %) +isoprenoid (mol %). ²⁾Isoprenoid Content = Isoprenoid (mol %)/TotalUnsats (mol %).

When comparing polymerizations at −95° C., the blend of HFO-1234yf withMeCl produced butyl containing the lowest content of isoprenoid (Ex. 69& 70, Average=11%) as compared to polymerizations in pure MeCl diluent(see Table 8: Average=15%). The polymerizations performed in blends ofMeCl with HFO-1234yf also produced butyl with lower isoprenoid contentat −75° C. (Ex. 61 & 62, Average=18%). The butyl material produced withthe blends of HFO-1234yf resulted in decreased isoprenoid content ascompared to 100% MeCl at all temperatures.

Example G Increased Isoprene Content in Butyl Rubber

Series of polymerizations were also performed in 50/50 blends of MeClwith HFO-1234ze or HFO-1234yf under standard reaction conditions attemperatures ranging from −75° C. to −95° C. Table 12 lists the resultsof polymerizations conducted in mixtures of the fluorinated diluentswith MeCl at various temperatures ranging from −75° C. to −95° C.

TABLE 12 Isoprene MeCl/ Reaction Content in Total Diluent Vol Temp FeedConversion Mw Unsats¹⁾ Ex. Blend (%) (° C.) (mol %) (Wt. %) ×10³ Mw/Mn(mol %) 71 HFO-1234ze 50/50 −75 2.3 25 145 4.18 1.20 72 HFO-1234ze 50/50−75 2.3 12 106 1.83 1.08 73 HFO-1234ze 50/50 −80 2.3 19 94 5.65 1.22 74HFO-1234ze 50/50 −80 2.3 21 108 5.69 1.19 75 HFO-1234ze 50/50 −85 2.3 24136 5.71 1.30 76 HFO-1234ze 50/50 −85 2.3 27 120 5.30 1.57 77 HFO-1234ze50/50 −90 2.3 31 165 4.02 1.51 78 HFO-1234ze 50/50 −90 2.3 29 135 5.171.63 79 HFO-1234ze 50/50 −95 2.3 33 243 4.18 1.39 80 HFO-1234ze 50/50−95 2.3 42 238 4.13 1.46 81 HFO-1234yf 50/50 −75 2.3 88 310 4.89 1.45 82HFO-1234yf 50/50 −75 2.3 89 275 5.18 1.42 83 HFO-1234yf 50/50 −80 2.3 82229 3.07 1.47 84 HFO-1234yf 50/50 −80 2.3 77 222 3.03 1.53 85 HFO-1234yf50/50 −85 2.3 74 305 3.06 1.58 86 HFO-1234yf 50/50 −85 2.3 73 300 2.891.65 87 HFO-1234yf 50/50 −90 2.3 69 354 3.01 1.50 88 HFO-1234yf 50/50−90 2.3 77 348 2.94 1.60 89 HFO-1234yf 50/50 −95 2.3 75 458 4.61 1.74 90HFO-1234yf 50/50 −95 2.3 62 455 5.02 1.62 ¹⁾Total unsaturations =1,4-isoprene (mol %) + isoprenoid (mol %).

As seen in Table 12, data for mixed diluent systems of fluorinatedsolvents with MeCl follows similar trends to the data presented inTables 1 and 2 for the pure diluent polymerizations. At similarconcentration of isoprene in the reaction feed, the MeCl/HFO-1234yfblend produced polymer with higher total isoprene incorporation thanpolymerizations performed with blends of MeCl with HFO-1234ze at alltemperatures lower than −75° C. Polymerizations performed in blends ofMeCl with HFO-1234yf resulted in the highest level of polymerunsaturation at all temperatures, similar to the results observed in thepure diluents.

The incorporation of isoprene was compared based on the ratio of feedmonomer composition (f=[M₁]/[M₂]) to copolymer composition(F=[M₁]/[M₂]). It is well known in the literature that the rateconstants for the copolymerization of 2 monomers can be described inQuirk RP, Gomochak-Pickel DL.; The Science and Technology of Rubber, 3rdEd., Chap. 2.

-   -   M₁*+M₁→M₁* (rate=k₁₁)    -   M₁*+M₂→M2* (rate=k₁₂)    -   M₂*+M₂→M2* (rate=k₂₂)    -   M₂*+M₁→M₁* (rate=k₂₁)

The monomer reactivity ratios are derived from the rate constants asfollows, and express the relative reactivity of each of the two types ofgrowing chain ends with their ‘own’ monomer type as compared with the‘other’ monomer:

r ₁ =k ₁₁ /k ₁₂ ; r ₂ =k ₂₂ /k ₁₂

The instantaneous composition of the copolymer relative to the feedmonomer concentrations can be determined using the following Mayo-Lewisequation:

$\frac{d\left\lbrack M_{1} \right\rbrack}{d\left\lbrack M_{2} \right\rbrack} = \frac{\left\lbrack M_{1} \right\rbrack \mspace{14mu} \left( {{r_{1}\left\lbrack M_{1} \right\rbrack} + \left\lbrack M_{2} \right\rbrack} \right)}{\left\lbrack M_{2} \right\rbrack \mspace{14mu} \left( {{r_{2}\left\lbrack M_{2} \right\rbrack} + \left\lbrack M_{1} \right\rbrack} \right)}$

where:

f=[M ₁ ]/[M ₂] (monomer feed ratio)

F=d[M ₁ ]/d[M ₂] (copolymer composition)

In the case where r₁>>1>>r₂ a drift in the composition of the polymerformed throughout the reaction will occur, with monomer 1 beingpreferentially added early in the reaction. The second monomer willreact more during the later stages of the polymerization once monomer 1is mostly consumed. Indeed, it is well known that the reactivity ratiosfor an isobutylene/isoprene copolymerization in MeCl is r₁=2.5 andr₂=0.4, resulting in an f/F ratio close to 0.6. To achieve a more randomcopolymer the reactivity ratios should be equal and close to 1.(r₁=r₂=1) In this limiting case, the f-ratio (f/F) will be closer to1.0.

Table 13 lists the results of polymerizations conducted in pure diluentsat −95° C. with feed isoprene contents in the range from 2.3 to 8.6 mol%. Similar to the examples in Table 12, rubber produced at −95° C. usingHFO-1234yf as diluent contains significantly more unsaturation fromincorporated isoprene than compared to the other diluent systems at allfeed isoprene contents. FIG. 5 compares the feed and copolymer monomerratios (f-ratio) for the polymerizations in pure diluents at −95° C. Itis observed that the fit line through the data gives an f-ratio of 0.88for the butyl copolymer produced in HFO-1234yf. In comparison thef-ratio fit line for HFC-134A is 0.74 and for MeCl is 0.58. Therefore,it is clear that the reactivity ratios in HFO-1234yf are more closelymatched resulting in an increased incorporation of isoprene during thepolymerization and thus a more random copolymer. HFO-1234yf results inan increased incorporation of isoprene (f/F=0.9) as compared to HFC-134A(f/F=0.8) or MeCl (f/F=0.6).

TABLE 13 Feed Isoprene Total Content f Conversion Unsats¹⁾ F Ex. Diluent(mol %) ([M₁]/[M₂]) (Wt. %) (mol %) ([M₁]/[M₂]) f/F 91 CH₃Cl 2.3 42.3 801.34 73.6 0.57 92 CH₃Cl 4.5 21.2 38 2.69 36.17 0.58 93 CH₃Cl 5.6 16.9 713.42 28.24 0.60 94 CH₃Cl 6.6 14.1 40 4.14 23.15 0.61 95 CH₃Cl 8.6 10.672 5.71 16.51 0.64 96 HFC-134A 2.3 42.3 58 1.63 60.4 0.70 97 HFC-134A3.4 28.2 51 2.85 34.1 0.83 98 HFC-134A 4.5 21.2 48 3.98 24.1 0.88 99HFC-134A 5.6 16.9 54 5.00 19.0 0.89 100 HFO-1234yf 2.3 42.3 87 1.99 49.20.86 101 HFO-1234yf 3.4 28.2 22 2.95 32.9 0.86 102 HFO-1234yf 4.5 21.243 4.32 22.2 0.96 103 HFO-1234yf 5.6 16.9 47 5.40 17.5 0.97 ¹⁾Totalunsaturations = 1,4-isoprene (mol %) + isoprenoid (mol %).

The novel features of the present invention will become apparent tothose of skill in the art upon examination of the detailed descriptionof the invention. It should be understood, however, that the scope ofthe claims should not be limited by the preferred embodiments set forthin the examples, but should be given the broadest interpretationconsistent with the specification as a whole.

1. A copolymer of at least one isoolefin monomer and at least onemultiolefin monomer and/or β-pinene monomer, the copolymer having anisoprenoid content lower than an isoprenoid content of a comparablepolymer produced in a butyl rubber slurry process using1,1,1,2-tetrafluoroethane as a diluent.
 2. The copolymer according toclaim 1, wherein the isoprenoid content is less than 15%, preferableless than 12%, preferably 11% or less, or preferably 6% or less based ontotal unsaturations in the copolymer.
 3. The copolymer according toclaim 1, wherein the copolymer is produced by contacting the at leastone isoolefin monomer with the at least one multiolefin and/ortheβ-pinene monomer in the presence of at least one Lewis acid and atleast one initiator in a diluent at a temperature of less than or equalto −75° C., or less than or equal to −95° C., and the diluent comprisesa hydrofluorinated olefin (HFO), wherein the HFO comprises at leastthree carbon atoms and at least three fluorine atoms.
 4. The copolymeraccording to claim 3, wherein the HFO comprises1,3,3,3-tetrafluoro-1-propene (HFO-1234ze),2,3,3,3-tetrafluoro-1-propene (HFO-1234yf) or mixtures thereof.
 5. Thecopolymer according to claim 3, wherein the HFO comprises2,3,3,3-tetrafluoro-1-propene (HFO-1234yf).
 6. The copolymer accordingto claim 1, wherein the at least one isoolefin monomer comprises anisoolefin having from 4 to 16 carbon atoms or preferably 4 to 7 carbonatoms.
 7. The copolymer according to claim 1, wherein the at least oneisoolefin monomer comprises isobutene, 2-methyl-1-butene,3-methyl-1-butene, 2-methyl-2-butene, 4-methyl-1-pentene or mixturesthereof.
 8. The copolymer according to claim 1, wherein the at least onemultiolefin and/or β-pinene monomer comprises a muitiolefin having from4-14 carbon atoms.
 9. The copolymer according to claim 1, wherein the atleast one multiolefin and/or β-pinene monomer comprises isoprene,butadiene, 2-methylbutadiene, 2,4-dimethylbutadiene, piperyline,3-methyl-1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene,2-methyl-1,5-hexadiene, 2,5-dimethly-2,4-hexadiene,2-methyl-1,4-pentadiene, 2-methyl-1,6-heptadiene, cyclopentadiene,methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene ormixtures thereof.
 10. A process for producing a copolymer, the processcomprising: contacting at least one isoolefin monomer with at least onemultiolefin monomer and/or β-pinene monomer in the presence of at leastone Lewis acid and at least one initiator in a diluent comprising ablend of a saturated hydrofluorocarbon and an inert solvent other thanthe saturated hydrofluorocarbon.
 11. The process according to claim 10,wherein the saturated hydrofluorocarbon comprises1,1,1,2-tetrafluoroethane.
 12. The process according to claims 11,wherein the inert solvent comprises a halogenated hydrocarbon.
 13. Theprocess according to claim 11, wherein the inert solvent comprisesmethyl chloride.
 14. The process according to claim 10, wherein theblend comprises a 10-90/90-10 v/v mixture of the saturatedhydrofluorocarbon and the inert solvent.
 15. The process according toclaim 10, wherein the blend comprises a 50/50 v/v mixture of thesaturated hydrofluorocarbon and the inert solvent.
 16. The processaccording to claim 10, wherein the at least one isoolefin monomercomprises isobutene.
 17. The process according to claim 10, wherein theat least one multiolefin and/or β-pinene monomer comprises isoprene. 18.A copolymer produced by the process as defined in claim
 10. 19. Theprocess according to claim 10, wherein: the at least one isoolefinmonomer and the at least one multiolefin and/or β-pinene monomer providea monomer total monomer weight, and the at least one isolefin comprises85% to 97% of the total monomer weight, and the at least one multiolefinmonomer and/or β-pinene comprise 3.0% to 15% of the total monomerweight; the at least one isoolefin monomer comprises isobutene; the atleast one multiolefin and/or β-pinene monomer comprises isoprene; theLewis acid is selected from a group consisting of ethyl aluminumdichloride (EADC), diethyl aluminum chloride (DEAC), titaniumtetrachloride, stannous tetrachloride, boron trifluoride, borontrichloride, methylalumoxane, and; mixtures thereof; the initiatorcomprises a cationogen and/or a proton source selected from a groupconsisting of water, hydrochloric acid (HCl), alcohol, phenol, thiols,carboxylic acids and mixtures thereof; the saturated hydrofluorocarboncomprises 1,1,1,2-tetrafluoroethane; the inert solvent comprises methylchloride; the blend comprises a 50/50 v/v mixture of the saturatedhydrofluorocarbon and the inert solvent; and the contacting is done at atemperature of less than or equal to −95° C.
 20. The copolymer accordingto claim 1, wherein: the at least one isoolefin monomer comprisesisobutene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene,4-methyl-1-pentene, or mixtures thereof; the at least one multiolefinand/or β-pinene monomer comprises isoprene, butadiene,2-methylbutadiene, 2,4-dimethylbutadiene, piperyline,3-methyl-1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene,2-methyl-1,5-hexadiene, 2,5-dimethly-2,4-hexadiene,2-methyl-1,4-pentadiene, 2-methyl-1,6-heptadiene, cyclopentadiene,methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene, ormixtures thereof; the isoprenoid content is less than 6% based on totalunsaturations in the copolymer; the copolymer is produced by contactingthe at least one isoolefin monomer with the at least one multiolefinand/or the β-pinene monomer in the presence of at least one Lewis acidand at least one initiator in a diluent at a temperature of less than orequal to −95° C., wherein: the diluent comprises2,3,3,3-tetrafluoro-1-propene (HFO-1234yf); the at least one Lewis acidis selected from a group consisting of ethyl aluminum dichloride (EADC),diethyl aluminum chloride (DEAC), titanium tetrachloride, stannoustetrachloride, boron trifluoride, boron trichloride, methylalumoxane,and mixtures thereof; the at least one initiator comprises a cationogenand/or a proton source selected from a group consisting of water,hydrochloric acid (HCl), alcohol, phenol, thiols, carboxylic acids andmixtures thereof.